When a person engages in physical activity, certain bodily process change, including pulse, breathing rate, blood pressure, and body temperature. In some circumstances, a user can carry a personal fitness tracking device, such as a pedometer, to track the user's activity levels over particular periods of time or throughout his or her normal daily activities. Such pedometer devices may be used to provide an estimate of the user's “steps” accumulated over time, the number of “staircases” climbed, and the number of calories used (which is usually calculated via an extrapolation calculation based upon the user's weight). In some cases, these estimated results can be displayed directly on the personal fitness tracking device or via a personal computing device. Such personal fitness tracking devices are commonly provided in a portable housing (including costly electronics and rechargeable batteries) that is mechanically clips to an article of clothing or carried in a pocket, which often leads to such devices being both costly and requiring reusability over many months or years.